Lidar technology can be used to obtain three-dimensional information of an environment by measuring distances to objects. A Lidar system may include at least a light source configured to emit a pulse of light and a detector configured to receive returned pulse of light. The returned pulse of light or light beam may be referred to as echo light beam. Based on the lapse time between the emission of the pulse of light and detection of returned pulse of light (i.e., time of flight), a distance can be obtained. The pulse of light can be generated by a laser emitter then focused through a lens or lens assembly. The returned pulse of light may be received by a detector located near the laser emitter. In some Lidar systems, such a pair of laser emitter and detector may be configured to rotate about a rotational axis thus scanning across a plane.
In some situations, in order to obtain sufficient three-dimensional information, multiple emitter/detector pairs may be employed. Such Lidar may also be referred to as multiline Lidar. A multiline Lidar may provide benefits of achieving a large field of view or greater resolution. A large area scan can be achieved by rotating Lidar and thereby rotating the vertical field of view with the Lidar. In some cases, the multiple emitter/detector pairs may be arranged into arrays. The number and/or distribution of emitters arranged in a vertical direction (e.g., with respect to ground level) may substantially affect the angular resolution or angle range in the vertical field of view. For example, the vertical angular resolutions of 16-line, 32-line, and 64-line Lidars are 2°, 1.33°, and 0.43° respectively. In another example, the vertical angular resolutions of 4-line and 8-line Lidars are each 0.8°. The angular resolution or angle range may be limited by the spatial configuration of the emitters. For instance, as more laser lines are needed to achieve a higher vertical resolution, the overall Lidar system may have to increase the size to accommodate more laser emitters. In some cases, multiple emitters or lasers may be located at the focal plane of an optical assembly or optical lens which requires the emitters or lasers packed into a confined region of area. Such crowded or dense arrangement of the lasers may prevent excess heat generated by the lasers from being removed or dissipated from the Lidar system resulting in poor reliability of the Lidar system.